Abstract

Secondary electron yield (SEY or δ) limits the performance of a number of devices. Particularly, in high-energy charged particle accelerators, the beam-induced electron multipacting is one of the main sources of electron cloud (e-cloud) build up on the beam path; in radio frequency wave guides, the electron multipacting limits their lifetime and causes power loss; and in detectors, the secondary electrons define the signal background and reduce the sensitivity. The best solution would be a material with a low SEY coating and for many applications δ < 1 would be sufficient. We report on an alternative surface preparation to the ones that are currently advocated. Three commonly used materials in accelerator vacuum chambers (stainless steel, copper, and aluminium) were laser processed to create a highly regular surfacetopography. It is shown that this treatment reduces the SEY of the copper,aluminium, and stainless steel from δmax of 1.90, 2.55, and 2.25 to 1.12, 1.45, and 1.12, respectively. The δmax further reduced to 0.76–0.78 for all three treatedmetals after bombardment with 500 eV electrons to a dose between 3.5 × 10−3 and 2.0 × 10−2 C·mm−2.

This work was conducted under the aegis of the Science & Technology Facility Council (STFC) and Engineering & Physical Sciences Research Council (EPSRC) of the United Kingdom. Amin Abdolvand is an EPSRC Career Acceleration Fellow at the University of Dundee (EP/I004173/1).

Abstract

Secondary electron yield (SEY or δ) limits the performance of a number of devices. Particularly, in high-energy charged particle accelerators, the beam-induced electron multipacting is one of the main sources of electron cloud (e-cloud) build up on the beam path; in radio frequency wave guides, the electron multipacting limits their lifetime and causes power loss; and in detectors, the secondary electrons define the signal background and reduce the sensitivity. The best solution would be a material with a low SEY coating and for many applications δ < 1 would be sufficient. We report on an alternative surface preparation to the ones that are currently advocated. Three commonly used materials in accelerator vacuum chambers (stainless steel, copper, and aluminium) were laser processed to create a highly regular surfacetopography. It is shown that this treatment reduces the SEY of the copper,aluminium, and stainless steel from δmax of 1.90, 2.55, and 2.25 to 1.12, 1.45, and 1.12, respectively. The δmax further reduced to 0.76–0.78 for all three treatedmetals after bombardment with 500 eV electrons to a dose between 3.5 × 10−3 and 2.0 × 10−2 C·mm−2.